1. Field of the Invention
The present invention relates generally to optical elements, and more particularly to a non-Lambertian diffuser fabricated using mechanical means instead of light and mechanical methods for fabricating the diffuser.
2. Description of the Related Art
Methods for manufacturing and replicating optical components such as a master diffuser exhibiting desired light diffusing characteristics are well known. Many of these methods involve creating a master diffuser by exposing a photoresist material to a source of light and then replicating this master diffuser into one or more submasters of a more durable nature. Many of these methods inherently destroy the master diffuser when creating the submasters. There are also other methods of making replicas of a master diffuser which contain the optical features in the master without destroying the master diffuser. With each of these methods, the master diffuser is initially created optically. Submasters are created from these master diffusers utilizing a number of methods whereby the master diffuser surface is replicated into a submaster surface. These other methods are described in one or more pending U.S. applications, referenced below, which are assigned to the assignee of the present invention.
One such method involves creating a submaster for an optical product by recording optical features on a photosensitive medium using coherent or incoherent light. The photosensitive medium is then further processed to create a master optical product. A layer of two part silicone epoxy is then poured over the master to replicate the optical surface features of the master photosensitive medium in the silicone epoxy material. The silicone epoxy layer cures at room temperature and becomes rubber. The silicone material is then further cured and separated from the master to obtain a silicone rubber submaster. The soft silicone submaster is then used to make successive generations of submasters or final optical products by covering the soft submaster with a layer of epoxy, covering the layer of epoxy with a plastic substrate, curing the epoxy and separating the epoxy and plastic substrate from the submaster. This particular method of creating a diffuser is highly labor intensive, requires use of many different materials, requires performing a number of steps, and must be conducted in a sterile environment.
The specific embodiments described above regarding the rubber submaster and the silver and nickel submaster are disclosed in co-pending U.S. application Ser. No. 09/052,586 entitled "Method of Making Replicas While Preserving Master," commonly assigned to the assignee of the present invention.
Another method of creating a diffuser involves recording optical features in a photosensitive medium using coherent or incoherent light and then processing the medium to create a master. The photosensitive medium is then coated with a layer of silver. A layer of nickel is electroplated onto the silver layer and then the silver layer and layer of nickel are removed from the photosensitive material or medium to form the submaster. The combined silver and nickel backing form a metal shim submaster which is then replicated to fabricate final optical products by embossing the surface features of the submaster into epoxies, plastics or polycarbonate materials, or by injection molding such materials into a mold carrying the submaster. Again, this process is costly, labor intensive, wasteful of material and requires a sterile environment.
Another significant problem with each of these methods is that the submasters or final optical products created from the master optical elements are made from materials such as plastics, epoxies, or polycarbonate composites and exhibit relatively poor long-term characteristics. These materials are also not suited for use near extremely high temperature light sources because they have relatively low melting or softening temperatures when compared to other more durable materials.
Other commonly assigned U.S. patents and pending applications disclose somewhat related methods for making and recording optical products and replicating those products so that they may be mass produced. For example, U.S. Pat. No. 5,365,354 entitled "Grin Type Diffuser Based on Volume Holographic Material," U.S. Pat. No. 5,534,386 entitled "Homogenizer Formed Using Coherent Light and a Holographic Diffuser," and U.S. Pat. No. 5,609,939 entitled "Viewing Screen Formed Using Coherent Light," all owned by the present assignee relate to methods for recording and replicating optical products. Each of these U.S. patents is incorporated herein by reference for purposes including, but not limited to, indicating the background of the present invention and illustrating the state of the art.
Related U.S. patent application include Ser. No. 08/595,307 entitled "LCD With Light Source Destructuring and Shaping Device," Ser. No. 08/601,133 entitled "Liquid Crystal Display System with Collimated Backlighting and Non-Lambertian Diffusing," Ser. No. 08/618,539 entitled "Method of Making Liquid Crystal Display System," Ser. No. 08/800,872 entitled "Method of Making Replicas and Compositions for Use Therewith," and Ser. No. 09/075,023 entitled "Method and Apparatus for Making Optical Masters Using Incoherent Light." All the above applications are owned by the present assignee and are hereby incorporated by reference for purposes including, but not limited to, indicating the background of the present invention and illustrating the state of the art. Additionally, each of these patents and applications disclose methods of making optical products wherein the methods or the products exhibit many or all of the above-noted disadvantages.